Apparatus for the annealing of metals in continuous cold rolling



July 10, 1928. I

L. CAMMEN APPARATUS FOR THE ANNEALING OF METALS IN CONTINUOUS COLD ROLLING Filed April 19, 1928 gum INVENTOR. BY WWOd A TT 0RNEY.

Patented July 10, 1928.

UNITED STATES PATENT OFFICE.

LEON CAMMEN, OF NEW YORK, N. Y.

APPARATUS FOR THE ANNEAIING OF METALS IN CONTINUOUS COLD ROLLING.

Application filed April 19, 1928. Serial NO. 271,366.

This invention deals with means for annealing metal between passes in rolling, e. g. in continuous rolling of cold strip.

In the illustration,

Fig. 1 shows diagrammatically the general arrangement of the annealing set-up;

Fig. 2 shows in detail the switches 1ndicated as 12 in Fig. 1;

Fig. 3 shows a modification of Fig. 1.

While this process is applicable to a wide variety of metals and forms of rolling, this description, for the sake of simplicity and brevity, will be confined to its employment in connection with the cold rolling of steel strip. Any engineer familiar with the art will be able to adapt the machinery described here to such other problems in aunealing'as he may encounter.

When the metal in cold rolling of steel strip passes between the rolls, it becomes gradually harder and harder, until after a certain number of passes it becomes so hard that it must be annealed before further roll.- ing can be attempted. Annealing in'noncontinuous rolling is a simple matter, the material bein taken out of the rolls, e. g. in the form of coils, and placed in a furnace for a proper length of time. It is then taken out, cooled to t e proper temperature, and given a certain number of additional passes. This method of rolling and annealing which is common today, involves, however, a large amount'of handling of the material which becomes very costly when dealing with thin metal, such as gage QOand up and makes it impossible to take advantage of the economies of continuous rolling. To do this, it is necessary to anneal the strip as it goes through the mill, i. e. between passes, and no feasible way to do so has been discovered hitherto.

In the present. invention use is made of a phenomenon which, while generall well known, has never been applied to this kind of service. When an alternating current flowsthrough a conductor, secondary currents, known as eddy or Foucault currents,

are established in those parts of outside coninterlinked 'motion several times and, e.

In the invention as shown the steel strip 1 goes from one pair of working rolls 2 to another pair of working rolls 10. One the way it passes through the interior of a coil 5 carrying a current of a character most suitable to produce a powerful secondary current in the strip 1, which means a current of proper high frequency and of suflicient output. Any electrical engineer knowing the dimensions of the strip and the range of temperatures desired can calculate the frequency and energy input into coil 5 without any trouble.

The advantage of using eddy currents for heating the strip lies in the following; first, as compared with heating by electric current by the resistance method (which has been tried and failed), there can be no arcing between the contact elements and the strip and hence there are no burned spots on the surface of the strip which ruin its appearance; second, as compared with heating in a furnace by such means as gas: the heating is extremely rapid and does not depend on the heat conductivity of the surface and its ability to absorb radiation, both of which are poor in cold rolled strip. Furthermore, the method here described ensures a very uniform heating as the secondary currents fiow equally through every-part of the conductor, i. e. the strip.

Annealing consists however of two operations, raising the metal to the desired temperature to remove the hardness induced by cold working, and then lowering it again to the temperature proper for cold rolling. To attain this latter, the stri 1, after coming from the heating coil 5, is passed through cooling tank 7 filled with some. liquid (oil pr water) maintained at the proper temperaure. drastic cooling, the strip may be passed through two tanks in succession, as 7 and 8, v the former being filled with a hotter liquid than. the latter.

1 From the above it is obvious that 1n pass- 00 ing from working rolls 2 to working rolls 10, the strip must change the direction of its g., go down If it is desired to avoid excesslvely ductors which are magneticall with the alternating or pulsating flux. These secondary currents produce heating in the conductors through which they flow, and are therefore usually consideredobject-ionable. In this invention, useful work has been found for them.

into tank 7 and then come up again on its 0:; way to rolls 10. To do this, the arran ement consisting of a series of sheaves, sue as 3, with guards as 4, and push-pull rolls such as 6, has been provided, the pur ose of the push-pull rolls being merely to orward the no l 10, between the points 15 of strip along without etl'ecting any reduction in cross-section. this being the dillerence between the push-pull rolls and such Working rolls as 2 and 10. A set of squeegee rolls. such as 25, may be provided, to wipe off the strip an excess of oil that it may carry from the cooling tanks.

hen the rolling is just beginning and the strip has only passed the working rolls :2. it may be found that the mere push from the rolls 2 is insuflicient to carry it through the possibly fairly numerous bends and turns on the way rolls 10. The pushpull rolls, such as 6. help it then along. On the other hand. after the strip has entered the rolls 10, it is subjected to a powerful pull on the part of rolls 10 which may be quite sullicient (this isv a. matter of design) to pull the strip through the heating coil and tanks and take care of the friction encountered by the strip in doing this. In such a case, the power applied to the push-pull rolls would be wasted, and in fact the coordination of the effort exterted by the push-pull rolls with that exerted by rolls 2 and 10 might prove to be an additional and under the circumstances unnecessary complication. Means have been therefore provided to cut oil the power from the push-pull rolls as soon as the strip enters the. working rolls 10. These means are shown at 12 in Fig. 1, and in more detail in Fig. 2.

The switch 13 is so arranged that normally the points 15 make contact, and when they do so, the points 16 on both sides make contact with terminals 17 and close the circuit. permitting current from generator 18 to flow to the motor terminals 19 and 20, the motor supplying power to the pushpull rolls. \Vhen, however, as shown in Fig. 2, the strip 1 is pushed, as by the working rolls the switch, it makes the arms open and swin about the hinge pins 13, moving away fi'om terminals 17 and breaking the circuit between the generator 18 and the push-pull motor 19-20.

High frequency current is difiicult to generate efiiciently and its cost is therefore comparatively high. To save some of it, the arrangement shown in Fig. 3 has been designed. It is intended to be used only when oil is employed as a cooling medium. In the arrangement shown in Fig. 1. two tanks are used, 7 and 8, the oil in tank 7 being considerably hotter than in tank 8. In the arrangement shown in Fig. 3, an additional tank 21 is provided and oil is pumped to it from tank 7. This oil is presumably quite hot, and the strip 1 passes through tank 21 on its way to the heating coil 5, gaining some heat and thus reducing the currentdemand on coil 5. The sheaves, such as 3 in Fig. 1, and rolls, such as 6 in Fig. 1. are not shown here; neither are the pumps and accesses piping taking the oil from tank 21, as these are matters obvious to an engineer familiar with the present invention.

Should it be desirable to take special means to avoid oxidation of the strip during the period of heating in coil 5, the entire annealing machinery may be placed within a tank 9 filled with a neutral atmosphere, such as nitrogen or carbon dioxide. One of the advantages of the scheme shown in Fig. 3 is that the layer of oil which the strip carries from tank 21 protects it from oxida tion during heating in coil 5.

As the heating efiect of secondary currents is well known, no claim is made to its use for purposes of heating generally. All claims are confined to the employment of such currents for purposes of annealing in continuous cold rolling, and in this connection it may be remarked that while both rolling of cold strip and the heating of conductors by secondary currents have been known for many years, no one had thought of combining the two in a proper manner so as to achieve the very important result of making possible fully continuous rolling of cold strips.

The conductors in the coil 5 are shown as tubes. This is usually the case to permit water circulation through the coil for purposes of cooling.

I claim:

1. In an apparatus for continuous cold rolling of metals, two pairs of working rolls, adapted for the passage therebetween of a body of metal in the process of being rolled thereby, means for heating said body of metal while travelling between said two pairs of working rolls said means consisting of a coil surrounding in part said body of metal and carrying a high-frequency alternating current, and means for. cooling said body of metal while it is travelling between said two pairs of rolls.

2. In an apparatus for continuous cold rolling of metals, two pairs of working rolls, adapted for the passage therebetween of a body of metal in the process of being rolled thereby, means for heating said body of metal while travelling between said two pairs of rolls said means consisting of a coil surrounding in part said body of metal and carrying a high frequency alternating current.

3. In an apparatus for continuous cold rolling of metals, two pairs of working rolls, adapted for the passage therebetween of a body of metal in the rocess of being rolled thereby, means for heating said body of metal while travelling pairs of rolls said means consisting of a coil surrounding in part said body of metal and carrying a high frequency alternating current means for cooling said body of metal while it is travelling between said two pairs of rolls said cooling means consisting of a between said two vessel or vessels filled with liquid, and means for directing the body of metal from the first of said two pairs of rolls through the coil into and out of the liquid filled vessel or vessels, and thence to the second of said two pair of rolls.

4. In an apparatus for continuous cold rolling of metals, two pairs of working rolls, adapted for the passage therebetween of a body of metal in the process of being rolled thereby, means for eating said body of metal while travelling between said two pairs of rolls said means consisting of a coil surrounding in part said body of metal and carrying a high fre uency alternating current, means for cooling said body of metal while it is travelling between said two pairs of rolls said cooling means consisting of a vessel or vessels filledwith liquid, and means for propelling the body of metal from the first of said two pairs of rolls through the heating coil into and out of the liquid filled vessel or vessels, and thence to the second of said two pairs of rolls. 7

5. In an apparatus for continuous cold rolling of metals, two pairs of working rolls, adapted for the passage therebetween of a body of metal in the process of being rolled thereby, means for heating said body of metal while travelling between said two pairs of rolls said means consisting of a coil surrounding in part said body of metal and carrying a high frequency alternatin current, means for cooling said body 0 metal while it is travelling between said two pairs of rolls said coolin means consistmg of a vessel or vessel filled with liquid, and means for propelling the body of metal from the first of said two pairs of rolls through the heating coil into and out of the liquid filled vessel or vessels, and thence to the second of said two pairs of rolls, together with means for making said propelling means inactive when the said body of metal in the process of rolling passes through said second pair of rolls above referred to.

6. In an apparatus for continuous cold rolling of metals, two pairs of working rolls, adapted for the passage therebetween of a body of metal in the process of being rolled thereby, means for heating said body of metal While travelling between said two pairs of rolls said means consisting of a coil surrounding in part said body of metal and carrying a high frequency a ternating current, and means for coating said body of metal Witha liquid film while said. body is travelling from the first of said two pairs of rolls to the heating coil above referred to.

Signed in New York, in the county and State of New York, April 17th, A. D. 1928.

LEON CAMMEN. 

